docs: def register(self, es, append=None, modulo=None):
          """register a `CMAEvolutionStrategy` instance for logging,
          ``append=True`` appends to previous data logged under the same name,
          by default previous data are overwritten.
  
          """
          if not isinstance(es, CMAEvolutionStrategy):
              raise TypeError("only class CMAEvolutionStrategy can be " +
                              "registered for logging")
          self.es = es
          if append is not None:
              self.append = append
          if modulo is not None:
              self.modulo = modulo
          self.registered = True
          return self